Magnetic Field Is the Dominant Factor to Induce the Response of Streptomyces avermitilis in Altered Gravity Simulated by Diamagnetic Levitation

Abstract

BackgroundDiamagnetic levitation is a technique that uses a strong, spatially varying magnetic field to simulate an altered gravity environment, as in space. In this study, using Streptomyces avermitilis as the test organism, we investigate whether changes in magnetic field and altered gravity induce changes in morphology and secondary metabolism. We find that a strong magnetic field (12T) inhibit the morphological development of S. avermitilis in solid culture, and increase the production of secondary metabolites.Methodology/Principal Findings S. avermitilis on solid medium was levitated at 0 g*, 1 g* and 2 g* in an altered gravity environment simulated by diamagnetic levitation and under a strong magnetic field, denoted by the asterix. The morphology was obtained by electromicroscopy. The production of the secondary metabolite, avermectin, was determined by OD245 nm. The results showed that diamagnetic levitation could induce a physiological response in S. avermitilis. The difference between 1 g* and the control group grown without the strong magnetic field (1 g), showed that the magnetic field was a more dominant factor influencing changes in morphology and secondary metabolite production, than altered gravity.Conclusion/SignificanceWe have discovered that magnetic field, rather than altered gravity, is the dominant factor in altered gravity simulated by diamagnetic levitation, therefore care should to be taken in the interpretation of results when using diamagnetic levitation as a technique to simulate altered gravity. Hence, these results are significant, and timely to researchers considering the use of diamagnetic levitation to explore effects of weightlessness on living organisms and on physical phenomena.

Impact of a High Magnetic Field on the Orientation of Gravitactic Unicellular Organisms—A Critical Consideration about the Application of Magnetic Fields to Mimic Functional Weightlessness

“…Various biological systems have been exposed to magnetic levitation ranging from cell cultures (e.g., Babbick et al, 2007;Hammer et al, 2009), bacteria (Dijkstra et al, 2011;Liu et al, 2011), and yeast (Coleman et al, 2007) to more complex systems, such as plants (Arabidopsis) and insects (Drosophila melanogaster) (Herranz et al, 2012), frog eggs (Valles et al, 1997), frogs (Berry and Geim, 1997), and mice (Liu et al, 2010).…”

Interrogation of Streptomyces avermitilis for efficient production of avermectins

“…Another technique called diamagnetic levitation has also been used to simulate the space environment for mutagenesis. 25 Diamagnetic levitation generates both a varying magnetic field and altered gravity. The individual effects of magnetic field and gravity were investigated for the first time, and the results demonstrate that the magnetic field is a more dominant factor influencing changes in morphology and avermectin production than altered gravity.…”

“…The individual effects of magnetic field and gravity were investigated for the first time, and the results demonstrate that the magnetic field is a more dominant factor influencing changes in morphology and avermectin production than altered gravity. 25 …”

Advances in engineered microorganisms for improving metabolic conversion via microgravity effects

“…The gramicidins (GS) produced by Bacillus brevis was higher when cultured in simulated microgravity bioreactor of RWV than in shaking flask [13]. Zhang L et al utilized the diamagnetic levitation to simulate an altered gravity environment and found that the secondary metabolite produced by Streptomyces avermitilis was increased at this culturing condition [19]. The dramatic shift in the site of MccB17 accumulation from E. coli ZK 650 to extracellular fluid when the cell growth took place in the low shear stress characteristic of simulated microgravity bioreactors [18].…”